Hemofiltration is increasingly used as a treatment of patients with acute renal failure and an alternative to dialysis. An infusion device must provide substitution fluid at a controlled lower rate than that of liquid removal for net reduction of body water. Hemofilter use is limited by decrease in ultrafiltration rate caused by protein build-up at the blood surface of the membrane. Application of suction to the ultrafiltration port increases ultrafiltration and hemofilter life, but eliminates otherwise automatic decrease of ultrafiltration with arterial pressure, risking an intolerable fluid removal rate. To alleviate the drawbacks, the development is proposed of an integrated modular system, containing all pumping and control devices to optimize hemofiltration, in a small and light package that can be mounted on a bed or litter. The hemofiltration control system includes a hemofilter pump, controlling ultrafiltration as a function of transmembrane pressure and arterial inlet pressure; a non-gravity-dependent infusion device, in which fluid replacement rate is controlled by an ultrafiltration rate signal from the hemofilter pump; and an in-line blood pump for use when arterial pressure is too low to provide adequate blood flow.